Is this to play with or just practice?
If just practice, then I would say a box of cheap lake balls will do as you will not be so worried about losing them or someone else picking them up by mistake.
If to play with I think you need to try as many different balls as you can and see which you get on best with.
Shows how long ago I last played, maximum handicap was 28/36 and even then you came across your fair share of bandits, having a HC of up to 56 is just mental in my opinion, how could a player like myself who practiced to get their club handicap down to 11 and society down to 6 ever compete with such high handicappers.
Personally If I had the chance to enter a competition with a handicap limit lower than my own, (bearing in mind I've not played for 16 years and expect no more then a 28 hc) I would either not bother or enter for the experience alone, as I think playing with better players helps improve your own game too.
Entry to comps may be limited by handicap normally for two reasons. 1) to limit the size of the field 2) to maintain the quality of entry (often done at county or national level)
But if neither of these apply and the club simply wants to prevent high handicappers winning, then they may limit the handicap for winning prizes (to 24 say) and allow entry to any player BUT the player's full handicap MUST be used for handicap purposes.